1. Field of the Invention
The present invention generally relates to, an organic electroluminescence (EL) device, more particularly to a full color organic electroluminescence (EL) display device, which enables light-emitting layers to be patterned by introducing a thermosetting light-emitting material and a light-to-heat conversion layer capable of converting light energy of a laser to heat energy and a method for manufacturing the same.
2. Description of the Related Art
In general, an organic EL display device is composed of several layers such as an anode, a cathode, a hole injecting layer, a hole transporting layer, a light-emitting layer, an electron transporting layer, and an electron injecting layer. The organic EL display devices may be classified into polymeric and small molecular types based on materials to be used, and each layer may be formed by vacuum deposition in the case of small molecular organic EL devices and by spin coating in the case of polymeric organic EL devices to form light-emitting devices.
In the case of single color devices, the organic EL device using the polymer may be simply fabricated using the spin coating process, however, it has a disadvantage that efficiency and lifetime are degraded in spite of a low driving voltage compared to the small molecular type.
When a full color device is fabricated, each of the red, green, and blue color polymers should be patterned, which causes luminous properties including efficiency and lifetime to be degraded when an inkjet printing method or a laser induced thermal imaging (LITI) method is used. In order to apply the LITI method, a light source, a transfer film, and a substrate are at least required, and light emitted from the light source should be absorbed by a light-absorbing layer of the transfer film, and should be converted to heat energy. The transfer materials of the transfer film should be transferred onto the substrate by means of the converted heat energy to form a desired image. (See U.S. Pat. Nos. 5,220,348, 5,256,506, 5,278,023, and 5,308.737 for its reference.)
The LITI method uses a donor film which is not a proper material when it is applied to a substrate with a complicated structure having stepped regions, and in particular, it is not preferable to use the donor film because external physical force is applied to surfaces of the substrate and the light-emitting layer when it is attached or detached thereto to thereby deteriorate interfacial properties. In addition, in the case of the polymer which forms the light-emitting layer, molecular weight is large so that adhesive strength of the film becomes higher after the LITI process is performed, which causes transfer properties to be deteriorated.
As a result, R, G, B patterning for the full color organic EL display device generally uses shadow mask technology to the latest, which is not suitable for patterning a large scaled display device.
In recent years, polymer types having a structure suitable for a photolithography process have been developed to pattern red, green, and blue light-emitting layers to fabricate the full color organic EL display device. However, in this method, a photo-acid generator which is blended to cure an exposed portion may cause impurities to infiltrate inside, and super acid resulted from curing may cause active materials to be damaged so that reliability or lifetime of the device may be adversely affected.